The present invention relates to a method for transferring of information related to a mobile subscriber which is moving within a cellular telecommunication system. The invention also relates to an arrangement for carrying out the method.
Updating of location information regarding a mobile subscriber which is moving within a cellular telecommunication system requires a variety of signalling. A cellular telecommunication system includes a home location register and a number of switching centres. Each switching centre controls a number of cells, a so called cell area. Subscriber data and location information related to the mobile is permanently stored in the home location register. The home location register is thereby able to direct an incoming call intended for the mobile subscriber to the correct location. When the mobile subscriber is present in a cell area which is controlled by a certain switching centre, subscriber data is temporarily stored adjacent to the switching centre at a visitor location register. Whenever the mobile subscriber moves between cell areas, the corresponding subscriber data follows, i.e. the data is downloaded from the home location register into the new visitor location register. The subscriber data is subsequently deleted in the previously visitor location register.
In present location updating procedures, the home location register acts as master while the switching centres/visitor location registers act as slaves. In case of a home location register failure, the total content of the home location register first have to be downloaded from a backup tape which stores relatively fresh traffic information. The information subsequently have to be downloaded from the home location register into the visitor location registers. In confined areas, e.g. capitals, with high voice or data traffic, signalling lines between the home location register and the visitor location registers are carrying a relatively low amount of signalling traffic. However, the total investment of the signalling lines between the home location register and the visitor location registers have to be dimensioned to be able to handle the updating of the visitor location registers in case of the rare situation of a home location register failure.
The European patent application EP 0 605 120 A1 provides means for cost reduction of signalling path""s lengths in selected areas.
In existing location updating procedures the home location register acts as master while the visitor location registers act as slaves. A cost problem arises since the signalling lines between the home location register and the switching centres often are long and since long signalling lines serving relatively low traffic are costly. Furthermore, in case of home location register failure, traffic information will have to be downloaded from a backup tape into the home location register and subsequently into the visitor location registers. Another cost problem thereby arises since the signalling lines between the home location register and the visitor location registers will have to be dimensioned to be able to handle the downloading. The traffic information which is downloaded into the visitor location register after the home location register failure will furthermore be somewhat out of date.
The problem is solved in accordance with the invention by modifying the location updating procedure so that the home location register acts as slave instead of master. The reversed master/slave relationship will reduce the costly signalling over long signalling lines. In case of home location register failure, downloading from the home location register to the visitor location register will be superfluous since the visitor location registers act as masters and consequently already are aware of the current traffic situation. The loading will now take place from the visitor location registers into the home location register. Since traffic path""s between the home location register and the visitor location registers will be unused shortly after the home location register failure, the loading can now take place over the traffic path""s.
The present invention thus relates to a method and an arrangement for transferring of subscriber specific data when the visitor location registers act as masters during the location updating procedure. Subscriber data, e.g. authentication data and service profile data, is permanently stored in the home location register and the data is temporarily stored in a first visitor location register in who""s cell area the mobile is present. When the mobile moves to a second visitor location register, the data is mainly transferred immediate from the first visitor location register to the second register, thereby in accordance with the invention reducing the involvement of the home location register significantly.
An object of the invention is to limit the number of necessary dedicated signalling path""s over long distances. Another object of the present invention is to reduce the network investment costs.
Another object is to integrate the signalling path""s into the larger traffic path""s.
Yet another object of the invention is to secure that no calls are lost during the location update procedure.
An important advantage is the reduction of costly long signalling path""s.
Another advantage afforded by the present invention is the reduction of network installation costs.
Another advantage is the simplification of the updating procedure in case of home location register failure. Another advantage of the invention is that the data in the visitor location registers after a home location failure still will be up to date.
Yet another advantage of the invention is the reduction of the signalling delay during the location update procedure.